You might have seen vortex generators – those little fins that protrude from the front of an airplane like the 737-800, or a Short Take Off and Landing (STOL) aircraft like this Top Cub. These little fins are amazing; they create vortices just like your wingtips do. How does that help? The vortices pull high energy air into the boundary layer, which delays a stall. They’re an integral part of many aircraft to lower stall speed – but did you know that they’re also used on transonic aircraft to keep control surfaces effective at high speeds? A few weeks ago, I posted about the boundary layer. It’s a layer of air right above the surface of your aircraft where skin friction slows down and removes energy from the airflow. As air flows across your wing, the pressure decreases until it reaches the center of lift – about 25% down the wing’s chord. Then, pressure starts to increase again, so the air moves from an area of low pressure to higher pressure – this is called an “adverse pressure gradient.” As the airflow moves towards high pressure, it loses energy. Eventually, when it runs out of energy, the airflow separates from the wing.
Author – Mohamed Freihat (C130/L100 , A&C approved consultant)
